摘要:

Effect of local cooling of the stem on exogenous 1AA transport from the apical bud and on the growth rate of axillary buds.Local cooling (1.5°C) of the stem (on 2 or 4 cm) ofVicia fabaL. cv. Aguadulce for 15 h stops the exogenous IAA transport from the apical bud and causes a high accumulation of tracers above and at the level of the cooled zone. This clamping effect is reversed after removal of the cooling system. If the cooling system is maintained for 48 h, about 25% of the exported radioactivity passes the cooled zone. However, the percentage IAA transmitted decreases to about 6.6% if the cooled zone is sufficiently wide (4 cm) and the temperature lowered to 0.7°C±0.3°C. Using a cooling system of 4 cm (0.7±0.3°C) partially releases the lowermost axillary buds (ax1and ax2) from apical dominance. Yet, the rate of growth of the axillary buds is generally lower than the growth rate after decapitation of the

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05036.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

A typical system comprising xanthine‐xanthine oxidase, which produces superoxide free radicals, significantly increased endogenous levels of the senescence‐associated lipoxygenase enzyme while cytokinin reversed this effect. It is suggested that in its interaction with free radicals cytokinin may have a dual effect: a) it may inhibit purine oxidation by the formation of a 2,8 dihydroxy purine which lowers the substrate affinity of xanthine oxidase; b) it may act as a direct free radical scavenger by virtue of H abstraction from the α‐carbon atom in the amin

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05037.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Protonemata of the mossFunaria hygrometrica(Hedw.) are grown in large amounts in a liquid culture system, allowing repetitive dry weight measurements for growth control. Ten‐day‐old protonemata are submitted to various light conditions, in the presence of a cytokinin (iP), which is known for its activity in bud initiation in the moss protonema. The hormone has no influence on the growth rate. Growth and budding are shown to be tightly related. Light is necessary for the initiation of buds but not for their development (to some extent). Identical protonematal growth can be obtained in white, Ted or blue light, but not budding, which is reduced in red or blue light. The early morphological changes in red light, known as nutations, and the presumed inhibitor in blue light could be responsible for the reduced budding. Bud initiation in the dark on an organic medium is greatly enhanced if red light pulses are given at regular intervals. When the latter are followed immediately by far‐red light pulses, the stimulating effect is partly suppressed, suggesting a phytochrome‐controlled process.Experiments with DCMU showed a peculiar effect of this herbicide, which inhibited the use of exogenous sugar in the light but not in t

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05038.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Nineteen soybean cultivars were grown for four weeks in controlled environmental chambers with artificial daylight supplemented by five UV‐B irradiance regimes to determine the range of growth and development responses of seedlings. Data from nine plant characteristics were assessed: leaf area, dry weight of leaves, stems and roots, total plant dry weight, height, ratio of roots to shoots and leaf area to weight and rating of leaves for damage. Significant differences were observed in the responses noted. Stunting, leaf chlorosis and loss of apical dominance were three general symptoms apparent on all cultivars which received UV‐B irradiance. Varying degrees of reduced leaf area and dry weight of the plants and altered ratios of weights of leaves per unit area and weight of roots to shoots were also found. It was concluded that different soybean cultivars demonstrate a marked difference in sensitivity to UV‐B radiation under the artificial conditions of controlled environmental growth chambers and this may indicate a genetic basis for variability in sensitivity of soybean cultivars to this waveband. However, the sensitivity to UV‐B radiation was increased by the lower than normal photon fluence of photosynthetically active radiation (225 μE

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05039.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

A study was made of the effects of salinity on the concentrations of free sugars, glycinebetaine, proline and other chemical components ofAster tripoliumL.,Daucus carotaL.,Honkenya peploides(L.) Ehr. andPlantago coronopusL. (Dicotyledones); andCarex extensaGood.,Eleocharis uniglumis(Link) Schutt.,Juncus maritimaLam. andSchoenoplectus tabernaemontani(C. C. Gmel.) Palla (Monocotyledones) grown in the laboratory. InPlantago coronopusthe level of the polyol sorbitol increased when the plants were subjected to NaCl stress, while inHonkenya peploidesthe cyclitol pinitol accumulated. No consistent pattern emerged with respect to the changes in free sugar contents in either the monocotyledonous or dicotyledonous plants, though the monocotyledonous plants generally had higher sugar contents.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05040.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

During stratification at 5°C indole‐3‐acetic acid (IAA) levels in embryos ofAcer platanoidesdecreased during the early stages but subsequently increased again throughout the remainder of a 144 day period. The reduction in IAA levels in embryos of fruits stored at 17°C was even more pronounced, and in addition, no increase was observed after longer storage periods at this temperature, the levels of IAA remaining very low. Germination in seeds maintained at 5°C was not observed until after 120 days or longer, but germination potential increased at an earlier stage, as shown by the fact that seeds transferred to 20°C gave appreciable increases in germination after much shorter chilling periods. Endogenous IAA levels in embryos from seeds transferred to 20°C after a chilling period, long enough to break dormancy, increased within 24 h,i.e.before visible germination, to levels similar to those observed in embryos from seeds chilled continuously for 144 days. Embryos from seeds chilled for 120 days,i.e.when the samples already showed visible germination and when the endogenous IAA content was already high, showed no further increase in endogenous IAA during a three day incubation at 20°C. None of the treatments employed was effective in inducing germination of seeds or embryos from fruits store

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05041.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Resting seeds of Scots pine contained a moderate amount of acid proteinase activity, about 90% of which was inhibited by pepstatin A and about 10% byp‐hydroxymer‐curibenzoate. In gel chromatography on Sephacryl S‐200 the proteinase activity showed a complex elution pattern with poorly separated peaks at positions corresponding to mol. wts. 100,000 and 30,000 and several shoulders. The results suggested that pine proteinases I and II, which are the main proteinases in the endosperms of germinating seeds (Salmia 1981: Physiol. Plant. 51: 253–258), were not present in the resting seeds.—Seedling extracts showed a low level of acid proteinase activity, which separated into several peaks in chromatography on Sephacryl S‐200. As none of the peaks had the catalytic properties of proteinase I or II, it seems that these endospermal enzymes are also lacking in the seedling tissues.—In the endosperms of germinating seeds the activity of the pepstatin‐sensitive acid proteinase(s) remained at a constant level throughout the period of reserve protein mobilization (lasting up to the stage when the length of dark‐grown seedlings was 60 mm). Proteinases I and II were absent from resting seeds, showed a small increase up to the 20‐mm stage, and then increased rapidly up to the 60‐mm stage.—Resting embryos contained relatively higher acid proteinase activity than resting endosperms, and again about 90% of it was inhibited by pepstatin A and about 10% byp‐hy‐droxymercuribenzoate. During germination the former activity decreased, the latter activity remained at approximately the same level, and the activity of the other acid proteinases increased continuously with the growth of the seedling.—It is concluded that the pepstatin‐sensitive proteinase(s), which is not affected by endogenous proteinase inhibitors, plays a central role in the initiation of reserve protein mobilization in both the embryo and the endosperm. Proteinases I and II, on the other hand, seem to account for the greater part of reserve protein breakdown in the main protei

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05042.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Fatty acid content of the triglycerides in subarcticDicranum elongatumSchleich was 4 times higher in low (1°C) than in high (23°C) temperature treated green tissue. The respective value was 3 times higher in low than in high temperature treated senescent portions of the shoot. Differences in the triglyceride concentration were corroborated with both light and electron microscopic observations. In addition, low temperature treatment resulted in thick cell walls and in an increase in dry weight of the tissue, whereas the opposite effects were caused by high temperature. Senescence of leaf tissue was accompanied by an over‐all decrease in membraneous cell structures. In senescent leaf cells an inner wall‐like layer, less electron dense than the thick secondary wall, was particularly well developed in low temperature treated material. Characteristic of the senescent leaf cells were cytoplasmic structures, which were described as dormant endos

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05043.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Esters of substituted phenoxy‐phenoxy propionic acid constitute a new class of herbicides that are effective against gramineous weed and crop species. Slight changes in chemical structure alter drastically the spectrum of weeds controlled by this class of herbicides. Wheat (Triticum aestivumL.) is resistant to diclofop‐methyl (methyl 2‐[4‐(2′,4′‐dichlorophenoxy)phenoxy] propanoate) (DM) and clofop‐isobutyl (iso‐butyl 2‐[4‐(4′‐phenoxy)phenoxy]propanoate) (CI), oat (Avena sativaL.) and wild oat (Avena fatuaL.) are susceptible to DM but resistant to CI, and corn (Zea maysL.) is susceptible to both compounds. The antagonism of IAA‐induced elongation in the coleoptile straight growth test was determined to measure biological activity of the herbicides. The basis for the differential responses by gramineous species was related to the metabolism and deioxication of the herbicides in coleoptiles. Growth of wheat coleaptiles was relatively unaffected by both compounds, oat coleoptile growth was inhibited by DM but not by CI. but corn coleoptile growth was inhibited equally by both compounds. Coleoptiles and excised shoots of the three species rapidly hydrolyzed both compounds to their respective acids (diclofop, clofop). The acids were conjugated to a water‐soluble ester conjugate or they were hydroxylated in the chlorine‐substituted phenyl ring and conjugated as a phenolic conjugate. Aryl hydroxylation is a detoxication mechanism in resistant plants. Plants resistant to DM or CI contained low concentrations of the parent ester and the free or bound (ester conjugate) acid and a high concentration of free or bound (phenolic conjugate) aryl hydroxylated acid in coleoptile and shoot tissues, Differential responses by the three gramineous species to DM and CI axe due apparently to differences in their detoxication mechanism. The enzyme for aryl hydroxylation in oat appears to have a higher affinity for the 4‐chloro‐ than for the 2,4‐dichloro‐substituted moiety. Therefore, oat hydroxylated clofop rapidly and was tolerant to CI but the limited ability of oat to hydroxylate diclofop resulted i

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05044.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Using an electric field pulse technique, we induced fusion between vacuoles and protoplasts ofKalanchoë daigremontiana, between protoplasts from etiolated and green leaf mesophyll, and between mesophyll protoplasts from plants of different physiological properties (Avena sativa: C3mechanism of photosynthesis,Kalanchoë daigremontiana: crassulacean acid metabolism). Close membrane contact amongst protoplasts or between protoplasts and vacuoles (as required for fusion) was achieved by the application of an alternating, non‐uniform electric field to the suspension. Due to the dielectrophoresis effect the cells attach to each other along the field lines. The fusion process is initiated by the injection of an electric field pulse of high intensity and short duration (μs range). The field intensity has to be sufficiently high to induce reversible breakdown in the area of close membrane contact. After the application of the field pulse, the fusion process is initiated and completed within seconds to a few minutes, depending on the material investigated.Fusion occurs between protoplasts and vacuoles as well as between protoplasts of different species. Both tonoplast and plasma membranes completely intermingled, indicating that in contrast to suggestions in the literature these membranes are compatible. Furthermore the cytoplasms of etiolated and green protoplasts obviously do not mix after fusion is completed, as etioplasts and chloroplasts kept separated from each other. In all experiments the volume of the fusion product equalled the sum of the compartments that underwent fusion. The wide spectrum of possible applications resulting from these fusion experiments in relation to metabolic problems is discu

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05045.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY